In a dynamic rigid disk storage device, a rotating disk, such as a magnetic disk, is used to store information. Rigid disk storage devices typically include a frame to provide attachment points and orientation for other components, and a spindle motor mounted on the frame for rotating the disk. A read/write element is formed on a “head slider” for reading and writing data from and to the disk surface. The head slider typically is supported and oriented relative to the disk by a head suspension assembly. The head suspension assembly provides both the force and compliance necessary for proper head slider operation. The head suspension assembly typically comprises a load beam and flexure, which can be attached to, or integrally formed with, the load beam. The head suspension assembly typically is attached to an actuator arm or E-block, which is in turn attached to an actuator. As the disk in the storage device rotates beneath the head slider and head suspension, the air above the disk also rotates, thereby creating an air bearing which acts with an aerodynamic design of the head slider to create a lift force on the head slider. The balance between the lift force and load force exerted by the head suspension substantially determines the distance, or “flying height” between the read/write head and the surface of the disk.
The trend in the evolution of dynamic rigid disk storage devices is toward higher data storage density, higher read/write speed, and a more efficient manufacturing process coupled with higher quality products. To achieve high data storage density, the read/write head must be close to the disk surface. That is, the flying height must be small. For example, for a data density of about 7.8 Gigabytes/cm2 or greater on a magnetic hard drive, the flying height of the slider is typically on the order of 10 nm or less.
To consistently attain such small flying heights, the performance parameters of the components of the suspension assembly must be controlled carefully. One parameter is the spring force or vertical load, often referred to as the “gram load”, that the head suspension assembly exerts on the slider head to balance the “lift” forces created by the air passing between the slider and the spinning disk. The gram load is typically set by the properties of the spring region (also referred to as the “radius region”) of the loadbeam. In a typical loadbeam, the spring region is a portion of reduced material thickness between a rigid load portion and a rigid mounting portion for attaching the loadbeam to an actuator. It is therefore desirable to have small variability in gram load. Depending on the spring portion forming process and the starting material used, the gram load may decrease to a lower level over time or as the loadbeam is deformed (“backbent”) beyond its designed normal operating range. It is desirable to reduce the amount of this decrease (“load loss”) and to reduce the manufacturing influence variability of the load loss. Another important parameter is the frequency response function (“FRF”), which is the amount of gain of the read/write head as a function of the frequency of an oscillating driving force, such as the force from the vibrations of a disk drive. Typically, the FRF has one or more resonant peaks over the range of frequencies of interest. That is, the head suspension resonates at certain frequencies. It is thus typically desirable to have fewer FRF peaks and to control their frequencies and gain at the intended rigid disk data storage devices operating frequencies. Generally, it is desirable to have FRF peaks of high frequencies, preferably higher than the operating frequencies of the storage devices.
In one common loadbeam manufacturing process, the thickness in the spring portion is reduced by chemically etching away part of the material in the spring portion. Ideally, the partial etching would proceed evenly, and the thickness of the remaining material (“remaining material thickness”, or “RMT”) would be uniform throughout the spring region. In reality, however, the etching rate is typically higher at the edges of the etching zone than at the center of the zone, as shown by the example illustrated in FIG. 11. As a result, the regions 1126 in the spring portion 1120 near the boundary between the spring portion 1120 and the mounting portion 1116, and between the spring portion 1120 and the load portion 1118, tend to be thinner than the middle portion 1128 of the spring region 1120. In a prior art loadbeam, the boundaries between the mounting portion and the partially etched spring portion and between the load portion and the spring portion are parallel to each other and parallel to the torque bending the loadbeam when the load force is applied to the head. In other words, the boundaries are perpendicular to the longitudinal axis of the loadbeam. With this configuration, gram load loss and product variability remain significant concerns. There is thus a need for a head suspension with improved characteristics, in particular reduced gram load loss and reduced variability in performance parameters.